We plan to continue our research on the visual pigments of vertebrate retinas. Microspectrophotometry (MSP) will be used to study rod, cone, macular and other pigments in single photoreceptors, groups of photoreceptors, and in sections of fresh and fixed retinal tissue. We plan to continue the study of human and monkey cone pigments to better define their absorption and bleaching properties, in detail, within the photoreceptor membranes and in extracts using several detergents. The goal of this work will be to determine the chromophore of each cone pigment including its structure and geometry (cis-trans isomers) and their spectral characteristics. Particular attention will be paid to regeneration and kinetic data using 11-cis retinal and other carotenoid analogs of the natural chromophores found to occur in these visual pigments. Human and monkey macular pigment will be studied using biochemical and chemical analyses which will be combined with MSP measurements to determine the state of macular pigment (Xanthophyll) molecules within the various cell layers of the fovea. The orientation of macular pigment in retinal cells will be measured with unpolarized and polarized light, in both fresh and fixed tissue. We need to know the distribution, as well as the exact location in retinal cells and cell membranes of this orientated Xanthophyll molecule. There are many possible reasons for its presence in the fovea and our goal is to investigate several aspects of its physiology. A new microspectrophotometer utilizing the latest developments in photon counting and imaging techniques (PIAS System, Hamamatsu Corp.) is being prepared which will have ultra high sensitivity. This new instrument will extend measurements of absorption spectra with unpolarized and polarized light into small areas of single cells, in membrane preparations and in detergent extracts. Human, monkey, and other vertebrate retinal research on both normal and diseased tissue will be studied with far more precise and less intrusive photon measurements. The application of these new techniques in our own research will allow us to study very small samples of tissue, to obtain both spectral and spacial information that has not been possible before.